First, replace the valve cover seal and the oil filler cap, both leak by this time and will dribble oil off both ends of the engine.

Rear seals on the 603 almost never leak -- they are a circular seal and the flywheel has to come off to replace them, so the trany has to come out (or the entire engine, since that is easier sometimes).

The head gaskets can fail on these engines and cause leaks, too.

You have something unusual going on, these cars are not known for leaks -- both the 603's my brother and I own use little or no oil in 6000 miles.

The drip on the bottom of the IP is fixable only be pulling the IP, a major pain. fuel on top is leaking pressure valve holder 0-rings, replace them and the seal (follow the proper torque sequence).

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!